I don't believe in karma; and I question whether free will truly exist.
Still it is a feeling thing, and I would say sure witches has been known to do hexes; just never heard of it as part of the wiccan path. But as I said it might be something I turned over in an alternate reality, and in this it is. With that said hexes is not a place you truly wish to go. You might find it necessarily the same way you might do some shielding; but as you said only because you see no other path to take. Like how an animal trapped in a corner probably most likely will attack because it is given no other option.
You could simply weave a new fate for your friend, and replace it with her old. If not sure, you can always ask the Fates to do it for you (or permission or guidance). They can be quite gentle if they see fit. With cutting ties then that is a question if you believe in all that karma thing; one could also say that your friend have gained more than enough contrast through this situation to know what she desires out of life
In the quantum field reality there is a potential reality where this is already solved; it could be as simple as using a spell to shift your consciousness into that reality.
Blessings are as powerful as hexes; so that should be equally as valid a path. You can bless that person in a way that their entire demeanor either changes, or they simply up and leave because they cannot stand being there. Like ever heard of the Norse God Baldr, his home Breidablik was said to be such that you could not stand to be in there if you had ill-content in your heart. So an idea might be that you set up a heart space around your friend, so when others enters it, if they have ill-content against her they will be trapped in the darkness of their own mind until they either turn away, or let go of their ill-content. I remember one becoming mad at me when she was speaking with me in my heart world, immediately a wind came and threw her out
